The long-term goal of this goal is to provide new information on the mechanisms by which gastrointestinal hormones (GIH) and calcium- regulatory peptides influence body function, particularly in the gut. We will study gene expression, synthesis, storage, transport and mechanisms of action of these agents on target cells, hormone-hormone interrelationships, target cell responses, and expressions of gene regulated by these agents. In the first project, we will study the effects that aging in the GI tract produces on gene expression patterns which contribute to functional alterations. We will define changes in gene expression patterns of hormones, their receptors, stress-related proteins and the effects of dietary alterations and gut location with aging. We will assess the functional effects of aging on gut and pancreatic growth. In the second project, we will examine the synthesis, processing and secretion of Luminal Cholecystokinin (CCK) Releasing Factor (LCRF) by epithelial cells of the gut and pancreas. We will characterize the biological activity of LCRF on CCK secretion and demonstrate that LCRF mediates physiologically relevant intestinal CCK secretion. In the third Project, we will examine the direct effects of bombesin (BBS) on activation of specific cell-surface receptors and intracellular signaling pathways to alter cellular programs of gene expression, and indirect actions by stimulating the release of bioactive agents that modulate the growth of normal and neoplastic cells of the GI tract. In the fourth Project, we will study the calcium-regulatory/cell growth peptide, parathyroid hormone- related protein (PTHrP) and determine its important regulatory roles in the gut and liver. We will identify and elucidate molecular mechanisms by which PTHrP functions in gut epithelium and hepatocytes utilizing GI and liver cells treated with exogenous PTHrP analogs or stably transfected with PTHrP cDNA in a sense or antisense orientation to study mechanisms and modes of action of PTHrP on cell proliferation and cell death (apoptosis). We will discern whether the protein acts in an intracrine fashion by targeting directly to the nucleus by autocrine/paracrine mechanisms following secretion. We will conduct our studies both in vitro and in transgenic mice that over- or under-express mechanisms following secretion. We will conduct our studies both in vitro and in transgenic mice that over- or under-express PTHrP in the gut and liver. We will express sufficient amounts of recombinant PTHrP to enable study of its 3D structure. Since the last competitive review we have demonstrated the productivity of our collaborating efforts by our publication: many publications relate to more than one project and utilize multiple cores. With the support of this grant, our studies have employed whole animals, cellular, subcellular and molecular models to define and understand mechanisms of actions of GIH in order to meet the long-term objectives of our program.